<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <button>按钮1</button>
    <button>按钮2</button>
    <button>按钮3</button>
    <button>按钮4</button>
    <button>按钮5</button>
    <script>
        var btns = document.getElementsByTagName('button');
        // 1.btns得到的是伪数组，里面的每一个元素btn[i]
        for (var i = 0; i < btns.length; i++) {
            btns[i].onclick = function() {
                for(var i = 0; i< btns.length; i++){
                    btns[i].style.background = '';
                }
                this.style.background = 'pink';
            }
        }
        // 2.首先排除他人，然后设置自己的样式 这种思想称为排他思想
    </script>
</body>
</html>